Memo to members of Congress: If you want to survive a scandal, make it philandering and not drugs.

Just ask Trey Radel, the freshman congressman who's getting ready to tender his resignation and head home to Florida, bidding adieu to colleagues like Senator David Vitter and Representative Mark Sanford. Radel—who famously billed himself as a "hip-hop conservative"—was busted in October for buying cocaine from an undercover officer in D.C.'s Dupont Circle neighborhood.

What followed is a case study in scandal management. When the news broke in November—to snickers—Radel adopted the time-tested suite of standard strategies: a tortured apology to his constituents, family, and colleagues; a leave of absence from Congress; and a spell in rehab to get himself straightened out. He was also sentenced to a year of probation for a misdemeanor cocaine possession charge.

As recently as two weeks ago, Radel seemed intent on returning to work and continuing his career. Yet today he'll resign from Congress after all, that contrition strategy not enough to save his House career. It's unclear what changed his mind, but a leading candidate is opposition from his home state. While Speaker John Boehner remained publicly silent on the matter, several Florida GOP officials demanded that Radel step down. His southeast Florida district is heavily Republican and is expected to stay in GOP hands when Governor Rick Scott schedules a special election. (National Journal has a great rundown on what to expect in that race.)

It's risky to draw too many conclusions about How We Scandal Now based on a single case, but the fact that Radel broke the law rather than his wedding vows seems important. It's also a warning for lawmakers that even as when half of Americans favor marijuana legalization, the country still takes a dim view of harder drugs and of its elected officials dabbling in narcotics. As my colleague Derek Thompson noted recently, "Although sex scandals clearly make for the easiest headlines, a 2013 studyfound that the most durable scandals are substantive rather than salacious." Perhaps it's worth amending that: The most durable scandals are substantive—or substances.